


You Don't Know Me

by FullOfBoredom



Category: Undertale (Video Game)
Genre: Bad Guy Poly - Freeform, Dustmare - Freeform, M/M, Multi
Language: English
Status: Completed
Published: 2021-01-24
Updated: 2021-01-24
Packaged: 2021-03-16 01:09:04
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,225
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28947942
Author URL: https://archiveofourown.org/users/FullOfBoredom/pseuds/FullOfBoredom
Summary: Nightmare can't have what he wants like a normal person. He has to brood on it for a while first...Thankfully, Dust understands.
Relationships: Bad guy poly
Comments: 6
Kudos: 49





	You Don't Know Me

“Boss, you can’t be serious right now.” Killer’s mouth hung open. Dust sighed off to his left, rubbing his face hard enough to shake dust from his hood. Horror wouldn’t meet his eyes, Cross also nervously avoiding them, leaving Error the only one still looking, albeit with some exasperation.

“I’m very serious.” Night responded to Killer without bending. “This is not something I’d like to be a part of.”

“If that’s the reason, cuz you don’t wanna, then that’s fine. But that sounds like a crock and I ain’t one for bullshit.” Killer grabbed the end of the table with whitened knuckles. Nightmare could taste the frustration off all of them, but his icy resolution could outlast their mounting agitation. “So just be honest. We can handle whatever you got to say.”

Nightmare looked at his phalanges, faking disdain with ease, unaffected stone face a talent he’d picked up before leaving the tree’s shade.

“I have no reason to lie. I am not willing to join your polyamorous posse.” They’d all been having “sleepovers” for months now, and he’d caught on long before he walked into a dream he wished he could erase. It would’ve been fine had it been Horror or Killer, but Dust was always vigilant and had remembered Nightmare’s brief intrusion the next morning. “I admit, it’s impressive you’ve managed to keep this working between so many of you, and I don’t care what you spend your free time doing, but my time will be spent on other ventures.”

“But in the dream-”

“I’m not a nun, but walking into a dream orgy when you expect something a little more tame and having a reaction isn’t that ridiculous.” Dust’s gaze bore into his skull. He couldn’t crack, not if he was trying to pass off this lie. Keeping calm was critical.

“So that’s it then. No?” Killer just shook his head. _Good, please, give up_. Nightmare’s feigned nonchalance had held through much worse, but the backlash afterwards would be worse if he broke beneath it.

“It’s a no.” Night stood from the little table he’d been called to like an intervention. “Now I’m returning to my study. Come find me if anything happens to the castle.”

He did NOT run, but he portaled the instant he turned a corner. It dropped him into a forest patch on the edges of this world just before he lost his composure.

“Son of a fucking BITCH!” His tentacles lashed out, splitting apart all the trees in the area with a giant swing. The corruption roared out of his mouth, furious and wild, screaming his voice hoarse. He didn’t give a damn about any of it, just seeing red from the blackened aura that got denser and denser around his body as he raged in nature, a force all on his own.

Of course he wanted to say yes! Envy scorched through his hands, clawing ahead for what it could not reach. Rage he reserved for himself, though saved some for his damned fate, at being too fucked to just be with a person. Even now, not within their embrace, the greed seduced his pitch black soul to have so many loves with which to indulge, having them all pay attention to him, _their king, their saviour, they OWED this to him!_

“God damn it, NO! Fuck you!” He continued ruining the countryside, rampant as the growth surrounding him.

He couldn’t love them. Not like they wanted, not the way they did each other, forever an outsider to the perfect temptation. He’d tip the balance and break the scales. He would destroy this for them. Slowly, he felt the brain fog raise, the tinges of red outlining everything finally fading away with his energy.

When the colors of the ruined forest fully returned, he directly portaled to his study. Dust was waiting patiently on the desk’s edge.

“The castle couldn’t have had a disaster that quickly.” Nightmare sat at his desk without acknowledging he’d been caught moping outside. Damn his perceptiveness when not distracted.

“I mean, it did.” Dust stated in a matter of fact tone. “They’re unhappy with the answer.”

“And what? You’re here to force me to change it?” Lashing out was what he excelled at. He wasn’t meant for soft cuddle puddles and doting, his body literal poison to those around him, his aura a drain. Dust didn’t bite.

“No. It wouldn’t be honest if it was forced.” He spoke airily, as if admitting the blatant truth could be anything but bitter disaster.

“Then why have you come to my study?” Nightmare hoped he’d rise to the bait that time, more direct in his aggression, and Dust would meet and rise to it most days, but besides twitching a few times, he holds his sanity at the low blow.

“To remind you. I know what I saw, and you know what I saw.” Dust didn’t leave room for argument and Nightmare didn’t lie about it out of respect. “Just know that the door is open should you change your mind.”

“Thank you, but my answer remains the same.” Damn him. Each denial took away more of his resistance. Perhaps he knew that, persistence hunting him with a strong will borne of the endless loops that forged most of his loyal following, waiting until one day he asked over something inconsequential like breakfast for the yes to slip out without Nightmare even on guard enough to catch it.

“Whatever you say Boss.” Dust nodded, but those eyes haunted him. He hadn’t heard the last of this, but the tide would ebb for now.

Nightmare fell back into the plush chair tiredly, already awaiting the next wave.

He knew what he wanted, but he could not obtain it. If he acted on his wishes, he’d destroy what he sought. And if he denied it, he’d be acting against his natural state while forcing himself to be miserable. There wasn’t a way to win that he could conceive of so he settled with ignoring the feeling entirely.

Despite his refusal, they didn’t change their interactions with him in the slightest after that first day.

Meal times remained largely unchanged except for the stolen glances at him if he betrayed any affection or laughed (which wasn’t often, but they were his crew and knew his weaknesses). Missions and responses to commands had also remained the same, though that was expected. They still offered him the opportunity to join in on movie nights. He had refused all of those since the rejection.

Maybe it was the way Horror had frowned when he’d said no for the fifth time in a row that changed his mind. Ignoring feelings didn’t make them disappear and he’d always been a little softer for Horror’s requests. He only asked for what he considered essential.

“Let me finish this. I’ll be down in five minutes.” Tidying up his papers took seconds, but he needed the minutes for composure.

When he made it down, Horror had curled up into Error’s lap with a gigantic grin, Error softly praising him with small head pets. The others waved at him.

“Hey Boss! Sorry, we let Cross pick this time.” The ‘ _we didn’t think you’d say yes_ ’ was implied. Nightmare nodded at Killer while moving to sit on the couch against the wall.

“I can live with choosing next time.” The little bursts of joy hit him like a face full of air freshener, his sludge rippling but otherwise unaffected. They’d popped in the DVD and set up before flicking off the lights.

Nightmare watched intently for the first fifteen minutes, he’d never seen it before, then looked around.

The group had paired off into cuddly duos, Killer and Cross, Horror and Error, leaving a lonely Dust seated by Nightmare. From here, he could feel Dust’s cold longing, wanting to join in like the others but knowing his only possible partner would refuse him. The movie was loud, the others absorbed in it or each other and not even able to see them from where they sat. Nightmare laid a tentative tentacle over Dust’s shoulder. He refused to speak a word, merely moving his arm for Dust to accept or not.

His dual colored eyes dilated before quietly shuffling over. Leaning in, he pressed himself along Night’s side with a little wiggle to get cozy.

From this angle, Dust’s ears within an inch of his mouth, he spoke softly.

“Is this okay?” He didn’t know what he felt like to others. Dust hummed so low that Night could only feel it.

“Yeah.” His right eye twitched, Papyrus must’ve said something. “What are those weird swords called?” Night’s eyes flicked up to the screen.

“A flamberge sword. It’s mostly used to counter others by-” Nightmare went into its varied history, a few famous wielders, its construction. They kept their eyes on the film, and Nightmare whispered it to Dust, like a secret history lesson while some cheesy dramatic scene full of loud music drowned out the rest. By the time he’d stopped, Dust comfortably leaned fully against him. His head had come into contact with the corner of Night’s mouth without ceremony, suddenly making Night aware of his proximity.

“You’ve read a lot.” Dust turned his head, now his teeth only a breath away. Nightmare couldn’t take his eyes off of them.

“Books were all I possessed before…” His eye roamed over the group before returning to the gentle intensity building in the centimeter between their teeth. “Dust…”

“You can have this Boss.” Dust’s soul pulsed with determination, Night washed over in its warm waters. “I know how much you wanted it.” His red and blue eyes dropped to Night’s teeth, hovering with hot breath, half-lidded in need. “Just take it Nightmare.”

The touch of their mouths made Night’s own soul explode in the rush of desire that blazed into an inferno at the smallest sprig of kindling. His tongue begged for entrance before he could think the action through, Dust letting it in without hesitation, shaky hands dug into Night’s sweater. The loud movie covered the quiet wet sounds, Night’s tentacles shifting silently to cradle Dust as he devoured all he was offered.

His soul lurched when he pulled back; he wanted to consume Dust but the rational part of his brain managed to catch him before he dove back.

“Hah. Nightmare, come back.” Dust’s hands had fisted in Night’s sweater tight enough to tear. Nightmare ignored it to squeeze his eye shut, trying to breathe through the mounting urge to take Dust apart, piece by piece, in view of the others, damn their relationship, _he’d take ANY of them whenever HE wanted._

“Stop.” He said it at normal volume, shouting compared to the hushed exchange before. It drew the attention of the others. “I can’t.”

“Why?” Nightmare hadn’t opened his eye to see, but he could hear how hurt Dust sounded, hands trembling where they still balled in each other’s clothes. His normally distracted voice spoke firmly. “Tell me why.”

“I can’t.”

“You can. You just won’t. Tell me why.” Dust shook his head to dislodge Papyrus, ringing in crystal clear. It struck his soul, shattering the thin barrier holding back his honesty, unable to hold onto thoughts while containing the rot of his corruption from spilling over and swallowing them whole.

“I will devour you. All of you.” His tentacles sought them out, tentative. His vocal cords ached with an involuntary voice drop. _“I will fucking ruin this. Your love cannot overcome my nature._ ” Each appendage curled around their throats, besides Dust, laying in his arms. The eye of the storm, Dust laid there calmly, like Nightmare’s tentacles weren’t threatening to strangle all of his loves in one fell swoop. Nightmare’s sludge dripped off of him, onto the couch, sizzling where it’d dropped onto Dust’s shins. He didn’t flinch.

“You wouldn’t know, you won’t let us try.”

He could feel the others struggling against him, hands sliding on the slick material while his tentacles grew tighter.

“ _I’LL KILL YOU!”_ Night growled, his own fingers clamping down on Dust’s neck, pressing down on the bone hard enough to creak underneath them. “ _I’ll take what I want and dust the rest!”_

“Then do it.” Dust met his eyes unafraid. He relaxed into the hold, even as Night’s hands got ever tighter.

The corruption buffeted the inside of his skull, whirlwind of thoughts and crazed emotion, fed by the slow building terror of the others, their struggles more and more frantic the longer his tentacles gripped them. The only exception was Dust. His eyes had slid shut, limp and relaxed in his hands. Nightmare didn’t realize how out of control it’d gotten until he heard the crack.

Nightmare released Dust instantly, hands struggling with the healing magic Nightmare was trying to force through the agitated sludge.

“Fuck, fuck, fuck, fuck!” Night didn’t stop trembling until he felt Dust touch his wrists. The splashes of cyan across Dust’s calm smile startled him out of everything, tentacles dropping the others to curl in on himself. With a deep breath, the magic flowed more evenly, in control of this at the very least. The crack slowly wove together until only a scar remained. Nightmare avoided the gazes of the others he could feel staring him down, caught unaware by Dust pulling on his wrists, falling directly onto Dust’s chest, face onto his shoulder, forced to stare at his own mistake.

“Just relax…” Dust’s head rested atop his own. He felt the skilled hands slide into the crevices between his tentacles, pressing and rubbing away the tight balls of tension until he finally let them all go.

“How did he do that?” Cross whispered from the side.

“Hell if I know.” Killer sounded close as well, shuffling from just beyond his vision.

“Patience.” Dust’s fingers pressed down to unwind the stress of his back, though not the sins crawling there. Nightmare shifted to lay in a way that he could see off the couch. The others watched them from the floor with wide eyes. He sighed, tracing Dust’s sternum during inhales.

“I could have killed you.”

“You wouldn’t have.” Dust’s faith never wavered, the others radiated guilt. Nightmare averted his gaze.

“I’m still sorry.”

“Then make it up to me.” Nightmare sat up, resting his hands on Dust’s chest for leverage, ending up sitting on his lap before taking the hands that had fallen off his back. He pulled Dust up to match him.

“How?” Night blushed under Dust’s intense observing, relaxing at the gentle clank he got in exchange. It sent a tremor through his spine.

“Answer us honestly.” Dust’s skull twitched against him, tranquil determination a temporary state at best. He kissed Night softly over and over again, plying at his defenses with the promise of what this could be, curiosity over how they worked together. Dust wasn’t alone in this after all. “Do you want us?” The shuffling of knees hit his ears; the others had moved closer to hear him, their hearts glowing with so much hope and positivity it almost hurt to bear. Night’s voice broke under its weight.

“…yes…” The next kiss was triumphant, his face cradled close while he submitted to Dust’s tongue. Dust broke them apart, Night too dazed to see, his hands reaching out to pull his partner back.

The taste changed, the tonguework different, enthusiastic all the same. The hand on his cheek this time larger, he felt a thumb stroke across the line beneath his ruined eye. The name was out before he saw them.

“Cross.” Behind, someone had made a home amongst his tentacles, a back against his. “That’s unusually bold of you.” His eye trailed over the purple flush with an amused grin. He didn’t let the building anxiety pool in the poor guardsman, grabbing the collar of his jacket to kiss him again while his tentacles wound around his other ‘attacker.’ Killer’s groans drifted to his ears.

“Fuck Nightmare, didn’t think you’d get so handsy so fast.” The back of his skull tapped Night’s. Tentacles had wound up Killer’s legs to hold them still, a third binding around his chest to keep him pinned. The fourth explored his upper femurs, pressing over his shorts to his pelvis, Killer’s gasps music to his ears. He pulled back from Cross with a smirk.

“You seemed like you’d be into it.” Killer nodded against his back, but Cross also nodded in front of him, eyelights blown wide with Night’s taste in his mouth and his hands on his chin, wiping away the line of purple saliva from that last messy kiss.

Horror leaned against his leg from the floor. Night dropped a hand to rub against his skull, avoiding the large crack without seeing, knowing the location by memory alone.

“Thanks.” Horror purred from the ground, head falling more heavily in his lap.

Sitting on Dust, Killer against his back, Horror in his lap, and Cross leaning over to kiss him and Dust equally brought his soul peace. Error hadn’t joined, but Nightmare would’ve been more surprised if he had.

“I-I’m sure y-you know my stance on t-t-touching by now.” Error had his arms crossed, body still pixelated near his neck from the impromptu strangling earlier.

“Except Horror. He deals with Horror’s touches the best out of all of us.” Cross removed himself from the pile to offer his hand. Error glared at the TV, but took it anyway. “Most of us have gotten to hand holding though!” Cross’s enthusiasm turned Error blue.

“S-shut up…” He offered his other hand for Cross to take as well, even Error unable to contain his smile at Cross’s joy and attention.

It was laughably easy, Nightmare slotted into the dynamic with ease, an extension of their regular back and forths but sweeter, tinged with something warm. The loud voice in his mind still craved more but he could fight it off for now. Nightmare took a deep breath.

“I’m…still concerned, about everything, but I…” They waited for him to collect his thoughts. “If you’ll have me anyway, then I’ll give it all I have.”

“That’s all we can ask.” Dust smiled while Horror hummed his agreement.

“Hell, that’s what we’re doing too. You, aaaah, ain’t special.” Killer’s body writhed against him. His tentacles hadn’t been distracted by the moment, steadily edging Killer into whining pants, shorts wet against his appendage and thrusting back against it. Night raised him up to hold him solidly between himself and Dust.

“You know, this does offer many new opportunities to shut you up.” His black bones traced the rim of Killer’s pelvis peeking out over the waistband. Killer cursed when Dust leaned forward against Killer’s back, circling to the front to tease his lower sternum, finger peeking inside of his rib cage.

“None of them work. Trust me, we’ve tried.” Dust hid his smirk against Killer’s back, playfully nipping through the hoodie, shaking against the charged bones.

“Fuck you guys.” Night met Dust’s dual-tone gaze one more time. Hesitant to accept and run forward with them still. But Dust took his hand to bring it with him into Killer’s body, wrapping them both around his spine to a moan. They’d help and guide him, he need only ask for it, and with that, he laughed.

“Maybe we will.”

**Author's Note:**

> Based off prompt of "You Don't Know Me" by Elizabeth Gillies.


End file.
